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LG 55LS4500 No Picture No sound No standby light

My LG 55LS4500 stopped working and I am looking for some help. The issue first started with the audio going out every once in a while and turning the TV off and on would fix the issue. Now the TV does not turn on. There is no stand by light on the bottom right of the TV. I tried the flash light trick in a dark room and did not see an image on the screen. I took out the backplate and broke out my multimeter. The power unit is supplying the standby 3.5V. Do you think the main board went bad?

Any help or advise would be appreciated.

Update (02/20/2019)

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Update (02/20/2019)

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checking the micom voltage.

Update (02/20/2019)

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Assuming that the clock is fine, this is where the first issue comes up. I get no voltage out of the pin 1. I am assuming there is no way to re-download the software without the TV being on so I guess replacing the main board is the next step, right? Or does anyone think that the power board is the issue?

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Evet Hayır
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So I checked the voltage as the picture shows and it showed 3.5V

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Checking pin 2 and pin 17 does not give me a voltage reading. It gives 0 volts so does that mean the power board is the reason why the TV is not turning on?

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Hi @godfather17

Here’s an image taken from the service manual for the TV showing the Power Up boot check flowchart.

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(click on image to enlarge for better viewing)

Here’s a link to the service manual for the TV.

To download the file, when the sentence below the Document preview box changes from This file is downloadable free of charge: ...processing... to This file is downloadable free of charge: Download, click on Download as this is the link. Be patient, it may take a little while to find the file.

If it is necessary, here’s a link to the firmware (and software upgrade guide)for the TV. Verify that your TV’s exact model number is listed in the Software File reference link, as installing the wrong firmware can brick the TV

Hopefully this is of some help.

Bu yanıt yardımcı oldu mu?

Evet Hayır
Puan 4

20 Yorum:

Thanks for the response but the power boot check does look like the one on the power board. I'll attach a picture of how my board power connector looks like and the order of the pins.

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Hi @godfather17 ,

Bit confused.

Did you follow the flowchart and check the voltages etc at the points mentioned?

Sheet 4 of the schematics shows the power detect circuit (p.29 in the pdf)

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I tried but got a little confused. I got as far as checking the standby voltage. I do not know what the micom is in order for to check what it is

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Hi @godfather17 ,

If you look at sheet 4 of the schematics top left hand corner is the "From LIPS and Power BD section.

It shows the +3.5V coming out of a 25 pin chip P403 via L404 which looks like it is an inductor given that its' designation is "L"

The flow chart say to check the voltage there at the inductor

if that is OK and presumably you don't have the gear to check the "clock" then go on and check if +3.3V is on pin 1 of the 25 pin chip P403 etc

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I may be getting over my head as I don't know how to check the voltage on the inductor

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